Glass fiber comes in various forms and can be used for a variety of applications. During the preparation of glass fiber, whether by blown fiber or continuous filament manufacturing process, the resulting glass fibers are easily degraded in their strength characteristics by the self-abrasive motion of one fiber passing over or interacting with another. As a result of this self-abrasion, surface defects are caused in the glass fiber filaments resulting in reductions in overall mechanical strength. Furthermore, glass fiber which is destined for use as building insulation and sound attenuation is often shipped in a compressed form so as to lower shipping costs. When the compressed bundles of glass fiber are utilized at a job site, it is imperative that the glass fiber product recover a substantial amount of its precompressed thickness; otherwise, loss of insulation and sound attenuation properties may result.
Fibrous glass insulation products generally comprise matted glass fiber bonded together by a cured thermoset polymeric material. Molten streams of glass are drawn into fibers of random lengths and blown into a forming chamber where they are randomly deposited as a mat onto a traveling conveyor. The fibers, while in transit in the forming chamber and while still hot from the drawing operation, are sprayed with an aqueous binder. A phenol-formaldehyde binder is currently used throughout the fibrous glass insulation industry. The residual heat from the glass fibers and the flow of air through the fibrous mat during the forming operation are generally sufficient to volatilize a majority of the water from the binder, thereby leaving the remaining components of the binder on the fibers as a viscous or semi-viscous high-solids liquid. The coated fibrous mat, which is formed in a compressed state due to the tremendous flow of air through the mat in the forming chamber, is then transferred out of the forming chamber to a transfer zone where the mat vertically expands due to the resiliency of the glass fibers. This vertical expansion is extremely important to the successful manufacture of commercially acceptable fibrous glass thermal or acoustical insulation products. Thereafter, the coated mat is transferred to a curing oven where heated air is blown through the mat to cure the binder and rigidly bond the glass fibers together.
Phenol-formaldehyde binders have been widely used since they have a low viscosity in the uncured state, yet form a rigid thermoset polymeric matrix for the glass fibers when cured. A low binder viscosity in the uncured state is required to allow the maximum vertical expansion of the coated mat when it exits the forming chamber. A binder which forms a rigid matrix when cured is required so that a finished fibrous glass thermal or acoustical insulation product, when compressed for packaging and shipping, will recover to its as-made vertical dimension when installed in a building.
Traditionally, fiberglass has been treated with phenol/formaldehyde resole binders to alleviate the previously-mentioned defects. The phenol/formaldehyde binder utilized in the past have typically been the highly alkaline resole type which have the combined advantages of inexpensive manufacture and water solubility. As discussed above, the binders are applied to the fiberglass from aqueous solution shortly after the fibers have been produced, and cured at elevated temperature in a curing oven. Under the curing conditions, any remaining aqueous solvent is evaporated, and the phenol/formaldehyde resole cures to a thermoset state. The fibers in the resulting fiberglass product are thus partially coated with a thin layer of thermoset resin, which tends to accumulate at the junctions where fibers cross each other. The resulting product therefore not only suffers from less self-abrasion, but also exhibits higher recovery than a fiberglass product not incorporating a binder.
The alkaline phenol/formaldehyde resoles contain a fairly large excess of formaldehyde from the manufacturing process. This excess of formaldehyde has been taken advantage of by adding urea to the phenol/formaldehyde resole, resulting in a urea-extended resole. Urea-extended phenol/formaldehyde binders are more cost-effective than the straight phenol/formaldehyde resins, but exhibit some loss in properties as the urea content increases. Thus, efforts have been made to incorporate other resins which can enhance the properties of the binder.
Insulation manufacturers have long desired an alternative polymeric binder system for fibrous glass products. However, low molecular weight, low viscosity binders which allow maximum vertical expansion of the mat in the transfer zone generally cure to form a non-rigid plastic matrix in the finished product, thereby reducing the attainable vertical height recovery of the finished insulation product when installed. Conversely, high viscosity binders which generally cure to form a rigid matrix in the finished product do not allow maximum vertical expansion of the coated, uncured mat. Thus it was desirous to prepare a non-phenol/formaldehyde binder having a low viscosity when uncured and structural rigidity when cured. This was solved in U.S. Pat. No. 5,318,990, which is herein incorporated by reference. That patent discloses a fibrous glass binder comprising a polycarboxy polymer, a monomeric trihydric alcohol and a catalyst comprising an alkali metal salt of a phosphorous containing organic acid.
In addition to the obvious improvements gained as a result of the U.S. Pat. No. 5,318,990 binder the industry also found that there were further improvements in terms of reducing emissions evolved during the coating and curing processes. To this end, binder formulations utilizing compounds such as polyacrylic acid have been used. Binders such as that are exemplified in U.S. Pat. Nos. 5,670,585 and 5,538,761, which are herein incorporated by reference.
The use of polyacrylic acid based binders, however, has resulted in severe problems involving high corrosion rates. Thus, there exists a serious need for a method of inhibiting and reducing the corrosion caused by these binder.